Re: [Haskell-cafe] Set monad

On Sun, Jan 9, 2011 at 7:45 AM, Sebastian Fischer wrote:

[...] Only conversion to the underlying Set type requires an Ord constraint.     getSet :: Ord a => Set a -> S.Set a     getSet a = a >>- S.singleton

this unfortunately also means that duplicated elements only get filtered out at the points where you use getSet, so in "getSet ((return 1 `mplus` return 1) >>= k)" k gets still called twice